1. Field of Invention
The integrated pump and sample vessel disclosed in this invention are typically used to take aliquot samples from hydrocarbon pipelines at any point from the producing well to the location of the end user.
2. Description of the Prior Art
High pressure pumps have been disclosed in U.S. Pat. No. 3,945,770 by Robert H. Welker. Improvements in this apparatus are further disclosed in U.S. Pat. No. 4,403,518 and pending applications Ser. No. 456,328, now U.S. Pat. No. 4,557,151 and Ser. No. 222,362, now U.S. Pat. No. 4,525,127 also by R. H. Welker. These pumps have been used to place odorants and hydrate inhibitors in natural gas pipelines; they have also been used in cryogenic service to pump liquid carbon dioxide. They have been used in other applications to pump various fluids, i.e., water.
Pumps of this type are widely used to take samples of natural gas for laboratory analysis of the BTU content of the natural gas. For many years, natural gas was sold merely by volume without regard to the BTU content. Today, almost every new contract involving the purchase or sale of natural gas will calculate the price based on both the volume and the BTU content. The volume of the gas is calculated by meter tubes, orifice plates and other means well known in the art. The BTU content of the gas is typically analyzed in a laboratory which is typically some distance from the well head, pipeline, or meter station. Samples are therefore taken and transported to the laboratory for analysis by calorimeter, gas chromatograph and other means well known in the art. It has therefore become extremely critical for the samples to be substantially representative of the product that is being bought or sold. A slight difference in BTU content can make an enormous difference in price.
The high pressure pumps of the prior art generally have a dead volume in the body of the pump between the point of sample collection and the outlet located on the valve body. This dead volume is typically increased because of the piping necessary to connect the sample vessel to the outlet on the pump. One object of the present invention is to eliminate any dead volume in the pump between the point of collection and the sample vessel.
When the high pressure pump as disclosed in the Welker '770 Patent was used to sample crude oil, there was no effective way to purge the dead volume in the valve body between samples. As a result, U.S. Pat. No. 4,440,032 was issued to Robert H. Welker for a sampler incorporating a purge system. Another object of the present invention is to eliminate the need for a purge system to flush the dead volume in the pump or the piping between the pump and the sample vessel.
Cylindrical sample collection vessels containing an internal piston which divides the vessel into two chambers have been used in the past in conjunction with pumps such as those disclosed in the aforementioned Welker Patents. Sample vessels similar to that shown in the present invention are disclosed in U.S. Pat. No. 4,459,865 by R. H. Welker. The subject of the present invention improves the design in the pump body and the sample vessel by integrating them into a single unit which eliminates dead volume between the point of collection of the sample and the sample container.
High pressure pumps of the type disclosed can create vacuums between various internal parts which may reduce the operational life of such internal parts. A vacuum breaker apparatus is disclosed in U.S. Pat. No. 4,470,773 which could be adapted for use in the present invention.